Fullerenes are a relatively recently discovered class of carbon-based materials and are spherical molecules with a “hollow” interior. Such cage-like structures can trap atoms and molecules inside. Such molecules are known as endohedral fullerenes. To date, some success has been achieved in encapsulating group III metals (Sc, Y), lanthanides (Ce, Gd, Pr, Ho and others), group II metals (Ca, Sr, Ba), group V elements (N, P) and noble gases (He, Ne, Ar, Kr and Xe) in fullerenes. The main problem for the commercial exploitation of these new molecules is their limited production and their unavailability in truly macroscopic quantities.
Existing methods for fullerene synthesis include the Krätschmer-Huffman method (W. Krätschmer, L. D. Lamb, K. Fostiropoulos and D. R. Huffman, Nature, 347, (1990) 354-358). By this method, graphitic carbon soot is produced by evaporating graphite electrodes in an atmosphere of helium; the soot is shown to contain fullerenes.
Endohedral fullerenes are generally sensitive to ambient conditions and a fullerene collection chamber for the anaerobic collection of fullerenes has been proposed by H. Shinohara (H. Shinohara, Rep. Prog. Phys., 63, (2000) 843-892), but the use of the proposed collection glove box has proved time consuming to use. There is considerable downtime for the apparatus while removing the soot from the collection chamber.
Moreover, in known arc discharge systems, a collection vessel may comprise a condensing wall which is cooled, for example, using liquid nitrogen. The hot carbon-containing vapour entering the chamber is cooled at the condensing wall and soot comprising the target carbon-containing compounds is deposited onto the condensing wall. In conventional collection vessels, a gas outlet is provided in the collection vessel. For example where helium gas flows into the collection vessel with the carbon-containing vapour, the helium gas exits the vessel through the outlet. The outlet is normally provided with a filter for capturing carbon-containing material which might otherwise pass through the outlet. It would be advantageous for more of the carbon-containing material to be deposited in the vessel rather than reaching the filter.
It is an object of one or more aspects of the present invention to solve or at least mitigate one or more of these or other problems. In particular, one or more aspects seek to provide a continuous or semi-continuous process for the production of fullerenes and other carbon-containing materials.